Pterosaur
'' was a type of pterosaur.]] Pterosaurs were flying reptiles that belonged to the order Pterosauria. They are unique has being the first group of vertebrates to evolve powered flight, existing from the late Triassic to the extinction at the end of the Cretaceous.Wellnhofer, P. (1991). The Illustrated Encyclopedia of Pterosaurs. pp. 557–560. ISBN 0-86101-566-5. They are often erroneously identified as dinosaurs. Description The pterosaur body plan was radically different from that of their reptilian ancestors in order to meet the requirements that flight presented. Wings The wings of pterosaurs were composed of skin membranes, and were attached the elongated fourth finger of each front limb. They were strengthened by small fibers called actinofibrils.Bennett SC (2000). "Pterosaur flight: the role of actinofibrils in wing function". Historical Biology 14 (4): 255–84. doi:10.1080/10292380009380572. Head Most pterosaurs had needle-like teeth situated in their jawsUnwin, David M. (2006). The Pterosaurs: From Deep Time. New York: Pi Press. p. 246. ISBN 0-13-146308-X., although some more advanced forms were toothless. Many individuals possessed keratinous beaks.Frey E, Martill DM (1998). "Soft tissue preservation in a specimen of Pterodactylus kochi (Wagner) from the Upper Jurassic of Germany". Neues Jahrbuch fu ̈r Geologie und Pala ̈ontologie, Abhandlungen 210: 421–41. Some pterosaurs are well known for their elaborate head crests. Nyctosaurus possessed a head crest measuring up to 55 centimeters in height, which is very large in comparison to the rest of the animal.Bennett, S.C. (2003). "New crested specimens of the Late Cretaceous pterosaur Nyctosaurus." Paläontologische Zeitschrift, 77: 61-75. Although crests were first thought to be limited to more advanced forms of pterosaurs, it has been shown through new fossil evidence and use of ultraviolet photography that even primitive pterosaurs had some type of crest on their heads.Czerkas, S.A., and Ji, Q. (2002). A new rhamphorhynchoid with a headcrest and complex integumentary structures. In: Czerkas, S.J. (Ed.). Feathered Dinosaurs and the Origin of Flight. The Dinosaur Museum:Blanding, Utah, 15-41. ISBN 1-932075-01-1. Integument Some pterosaurs were covered with integumentary filaments called pycnofibres (meaning "dense filament"Kellner, A.W.A., Wang, X., Tischlinger, H., Campos, D., Hone, D.W.E. and Meng, X. (2009). "The soft tissue of Jeholopterus (Pterosauria, Anurognathidae, Batrachognathinae) and the structure of the pterosaur wing membrane." Proceedings of the Royal Society B, published online before print August 5, 2009, doi:10.1098/rspb.2009.0846, which was similar to mammalian hair. Only a couple genera have been found to possess this, such as Sordes''Unwin DM, Bakhurina NN (1994). "Sordes pilosus and the nature of the pterosaur flight apparatus". Nature 371 (6492): 62–4. doi:10.1038/371062a0. and ''Jeholopterus, but they provide implied evidence that most or all pterosaurs were endothermic. Classification and Evolution In general, pterosaurs have been traditionally classified into two groups: Rhamphorhynchoidea and Pterodactyloidea (loosely defined as "primitive" and "advanced" pterosaurs, respectively). The origin of pterosaurs is not completely understood, although is has been proposed that they were a type of ornithodiran and thus closely related to dinosaurs and other archosaurs.Hone D.W.E., Benton M.J. (2007). "An evaluation of the phylogenetic relationships of the pterosaurs to the archosauromorph reptiles". Journal of Systematic Palaeontology 5 (4): 465–469. doi:10.1017/S1477201907002064. History The first pterosaur to ever be discovered, Pterodactylus, was originally described in 1784 as a type of sea creature.Collini, C A. (1784). "Sur quelques Zoolithes du Cabinet d’Histoire naturelle de S. A. S. E. Palatine & de Bavière, à Mannheim." Acta Theodoro-Palatinae Mannheim 5 Pars Physica, pp. 58–103 (1 plate). As better fossils were found and more people started to study them, however, it soon became clear that these were creatures designed for an aerial life. Paleobiology Flight Exactly how pterosaurs could fly is not yet understood and a point of contention. Some scientists have even claimed that it would be impossible for pterosaurs to stay aloft due to their body proportions.Alleyne, Richard (2008-10-01). "Pterodactyls were too heavy to fly, scientist claims". The Daily Telegraph (London). Retrieved 2010-05-22. Mark Witton has suggested that they used a vaulting mechanism to take off into the airHecht, Jeff (16 November 2010). "Did giant pterosaurs vault aloft like vampire bats?". NewScientist. Retrieved 2 March 2012., which would be an easy feat due to their powerful forelimbs."Why pterosaurs weren't so scary after all". The Observer newspaper. 11 August 2013. Retrieved 12 August 2013. Ground movement There used to be considerable debate whether pterosaurs were bipedal or quadrupedal when moving on the ground. However, pterosaur trackways have revealed that at least some species moved in a quadrupedal fashion.Hwang K, Huh M, Lockley MG, Unwin DM, Wright JL (2002). "New pterosaur tracks (Pteraichnidae) from the Late Cretaceous Uhangri Formation, southwestern Korea". Geological Magazine 139 (4): 421–35. doi:10.1017/S0016756802006647. Footprints from azhdarchids show that some pterosaurs walked with their legs almost vertically under the body, much like modern mammals and birds.Witton MP, Naish D (2008). "A reappraisal of azhdarchid pterosaur functional morphology and paleoecology". In McClain, Craig R. PLoS ONE 3 (5): e2271. doi:10.1371/journal.pone.0002271. PMC 2386974. PMID 18509539. Reproduction Pterosaur eggs are very rare, and have only been discovered in the past few years. The first known pterosaur egg was discovered in 2004 in Liaoning, China. The fact that the egg was flattened but not broken suggests that pterosaur eggs had leathery shells.Ji Q, Ji SA, Cheng YN, et al (December 2004). "Palaeontology: pterosaur egg with a leathery shell". Nature 432 (7017): 572. doi:10.1038/432572a. PMID 15577900. This hypothesis is supported by an egg from the pterosaur Darwinopterus found in 2011.Lü J., Unwin D.M., Deeming D.C., Jin X., Liu Y., Ji Q. (2011). "An egg-adult association, gender, and reproduction in pterosaurs". Science 331 (6015): 321–324. doi:10.1126/science.1197323. PMID 21252343. Analysis of pterosaur eggshell structure and chemistry has suggested that pterosaurs buried their eggs like modern turtles and crocodilians.Grellet-Tinner G, Wroe S, Thompson MB, Ji Q (2007). "A note on pterosaur nesting behavior". Historical Biology 19 (4): 273–7. doi:10.1080/08912960701189800. Baby pterosaur fossils are more common, and show that young animals were well developed and almost indistinguishable from adults besides their size.Bennett S. C. (1995). "A statistical study of Rhamphorhynchus from the Solnhofen Limestone of Germany: Year-classes of a single large species". Journal of Paleontology 69: 569–580. JSTOR 1306329. In popular culture Pterosaurs have been long depicted beside dinosaurs in popular culture, and are often mistakenly identified as dinosaurs. Unlike the dinosaurs, however, popular depictions of pterosaurs have remained largely unchanged since the 1960s.Hone, D. (2010). "Pterosaurs In Popular Culture." Pterosaur.net, Accessed 27 August 2010. The term "pterodactyl" is often used to describe these animals, although when used correctly the word is simply a name for Pterodactylus. References Category:Animals Category:Reptiles Category:Pterosaurs